Means for preventing interference



Get. 27, 1931.

' F. H. KROGER 29,5 3

IEANS FOR PREVENTING INTERFERENCE Filed Jan. 18. 1929 I291 awuewcoz FRED. H. KROGER 9% his wwjww Patented Oct. 27, 1931 UNITED;

PATENT OFFICE,

' FRED H. mm OF: RIDGEWOOD, NEW JERSEY, ASSIGNORTO, RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE,

MEANSYFOR PREVENTING INTERFERENCE Application filed January 18, 1928; Serial No. 333,481.

It is well known in the radio art that when an electrical device of any known character includes mechanism for making and breaking circuits carryin currents there accompanies the starting an stopping of current flow a setting up in the circuits of the mechanism and in the adjacent media an electrical transient which enerally is of such short duration as to a ect adjacent apparatus deb signed to operate at radio frequencies.

Usually, the transient is so rapidly damped out, that is, is of such high decrement that it has no definite oscillation frequency. Such a transient, however, although of short duration will affect radio apparatus in the vicinity thereof. Experiments have shown that even with a break between mercury electrodes in a vacuum with any combination of condensers, though the break is apparently I sparkless, it is accompanied by a transient.

Heretofore various methods have been used to prevent the transients set up in the above manner from disturbing radio apparatus located in the vicinity thereof. These meth- 5" ods which generally consisted in blocking out the transients by means of choke coils and in grounding the apparatus through condensers, usually failed in eliminating the disturbance.

Briefly and broadly, the object of: this invention is to provide a method of and apparatus for eliminating entirely the c'lfect of transients of the above nature on radio apparatus operating in the vicinity of said transients.

Another object of this invention is to provide interference preventing apparatus which may be applied to any electrical apparatus known today in which a make and break contact is used.

A further object of this invention is to provide devices for preventing such interference, which take the form of compact units having varying electrical characteristics which can be readily and economically manufactured and placed on the market.

The present invention in its broadest aspect comprises a choke coil and/ or condenser arrangement to be associated with the opening and closing contact in such a manner as to form therewith a miniature transmitter The constants ofithe inductances and/0r capacities of this device are so chosen as to change the frequency of the transient or rather to give the transient a definite predetermined frequency which will not interfere with adjacent radio apparatus.

The primary advantage to be attained by. the use-of a device constructed-in accordance with this invention is that interference caused by the; opening and closing contact of the electrical apparatus can be entirely eliminated'so that itdoes not: causeany undesired efiects whatsoever in adjacentradio receiving apparatus.

Another advantageto be gained by the use of units constructed in accordance with the present invention is that by means of the units of varying sizes the frequency of the transient may be fixed at any of a plurality of predetermined values, the frequency being:

so chosenrthat it will have no effect on radio apparatus in the vicinity.

Other objects and advantageswill become apparent from the following specification andtherefrom when read in connectionwith. the accompanying drawings in which:

Figure 1 shows diagrammatically'the circuit arrangement utilized'inalte'ringor giving to the'transient a definitepredetermined wavelength; while Figures 2 and 3show modifications of the apparatus shown in Figure 1.

Referring to the drawings, throughout which the apparatus necessary to carry out the method is represented by heavy lines and in which like reference charactersindicate like parts, 1 and 2 represent the electrical S. As will be seen from the drawings a complete oscillation circuit has been provided for the. member S which although termed a contact in the specification may e any known apparatus which tends to set up transients. The oscillation frequency of this circuit will be determined by the values of the inductances and capacities therein, which should be so chosen as to give the oscillations in said circuit a frequency which will not interfere with adjacent radio apparatus. To increase the effectiveness of the device the apparatus to be corrected and the correcting apparatus is maintained at ground potential by means of the conductor 7 connected between the condensers 5 and 6 and ground.

In some cases the lines or the apparatus itself may provide some of the inductance required to carry out applicants novel method. When this is so the oscillation circuit will be as indicated in Figure 2, in which the. inductance 8 represents the inductance of the line or of the apparatus which replaces the inductance 3 provided in Figure 1. In applying the novel method to apparatus of this nature only a single. inductance 4 and the condensers 5 and 6 are required to provide an oscillation circuit for S. In this case as in the first modification, the frequency of the oscillation circuit is determined by the values of the inductance 4 and capacities 5 and 6.

In the modification shown in Figure 3 which is otherwise similar in operation and arrangement to the first modification, it is assumed that the apparatus or lines provide suliicient inductance. These inductances represented by Figures 8 and 9 which replace the inductanoes 3 and 4 of Figure 1 are shunted by a pair of condensers 5 and 6 which complete the oscillation circuit. In all cases the entire apparatus is grounded by means of a grounded conductor 7 connected between the condensers.

In installing a filter system constructed in accordance with the present invention it is essential that the leads between the disturbing contact and the inductances and the leads between the inductance and the condensers be as short as possible, also that the inductances should be spaced at least one-half inch from metal on all sides, if possible, and that the connections from the terminals of the two condensers to ground be short and a good ground he used. 1

Although for purposes of illustration, I have described the at present preferred form of my invention, I do not wish to limit myself thereby except as marked out in the claims hereto appended.

I claim:

1. The method of preventing energy originating in apparatus, including an inherent source of transient energy, from impressing undesirable oscillations on adjacent radio apparatus which consists in including said source in an oscillation circuit and tuning said circuit to a frequency which will not affect the adjacent apparatus.

2. A method of preventing energy originating in apparatus, including an inherent source of transient energy, from setting up undesirable oscillations in adjacent radio apparatus which consists in confining said oscillations to a circuit tuned to a frequency which will not affect the adjacent radio apparatus.

3. The method of eliminating the influence of a source of transient energy on radio apparatus operating adjacent thereto which consists in providing an auxiliary circuit, including said source in said circuit, and tuning said circuit to a frequency at which the oscillations therein will not affect the adjacent radio apparatus.

FRED H. KROGER. 

